What Is Object-Oriented Programming Design?


Larry Thompson

Object-oriented programming (OOP) design is a programming paradigm that focuses on organizing code into objects, which are instances of classes. It provides a way to structure and manage complex software systems by encapsulating related data and behavior into reusable modules. This article will delve into the key concepts of object-oriented programming design and explain how it can be implemented effectively.

Classes and Objects

In OOP, a class serves as a blueprint for creating objects. It defines the properties (data) and behaviors (methods) that objects of that class will possess.

Objects, on the other hand, are instances of classes. They represent individual entities with their own unique set of data values.


class Car {
  String make;
  String model;
  int year;

  void startEngine() {
    System.out.println("Engine started!");

Car myCar = new Car();
myCar.make = "Toyota";
myCar.model = "Corolla";
myCar.year = 2021;
myCar.startEngine(); // Output: "Engine started!"

In this example, the class “Car” defines the properties (make, model, year) and behavior (startEngine()) of a car object. The object “myCar” is created using the “new” keyword and is assigned specific values for its properties.


OOP design promotes encapsulation, which means bundling data and methods together within a class to hide implementation details from the outside world. This ensures that data is accessed and modified only through predefined methods, known as getters and setters.


class BankAccount {
  private double balance;

  public double getBalance() {
    return balance;

  public void deposit(double amount) {
    balance += amount;

  public void withdraw(double amount) {
    if (amount <= balance) {